1. Field of the Invention
The present intention relates to color compensation of input images to display on a display panel.
2. Description of the Related Art
As known in the art, the color of an input image displayed by a display panel (e.g., liquid crystal display (LCD) panel or organic electric luminescence (EL) panel) differs from the color a viewer perceives of the displayed image. One of the causes of this difference is the influence of ambient light reflected by the display panel. That is, the image displayed is superimposed with the reflected light even if the display panel displays an image faithful to the input image. As a result, the viewer perceives the image as one that differs in color from the input image.
JP-A 2007-248936 (KOKAI) discloses an image processing apparatus that performs an image processing to improve the visual-recognition property of images displayed in a high-illuminance environment. More specifically, the apparatus converts an input video signal to a color space defined by hue, saturation and lightness, and increases the lightness and saturation in accordance with a rise in illumination, thereby enhancing the color contrast.
JP-A 2005-258404 (KOKAI) discloses a liquid crystal display in which the luminance of the backlight is increased in order to improve the visual-recognition property of images displayed in a high-illuminance environment.
The image processing apparatus of JP-A 2007-248436 (KOKAI) and the liquid crystal display of JP-A 2005-258404 (KOKAI) increase the lightness of the color space and the luminance of the backlight, respectively, thus correcting the image to enhance the visual-recognition property of images. Here arises a problem. The higher the reflection ratio of the display panel and the illuminance of ambient light, the greater the influence of the reflected light will be. The use of this image correcting method is inevitably limited. If this method is employed in devices (e.g., cellular phones) that may be used in high-illuminance environments (for example, in direct sunlight), hardware-related problems may occur. Further, this image correcting method is not desirable in terms of power consumption. Moreover, the image correcting method according to JP-A 2005-258404 (KOKAI) cannot be applied to display panels such as organic EL panels which have no backlights.